Books, papers and documents are often bound by a plastic binding element which has a spine and a plurality of flexible curl-shaped plastic rings. The rings extend through a series of holes punched along a common side of the pages of the stock. It is known to apply these plastic binders to a perforated stack by using a conventional binding machine that spreads open the binding element to uncurl the rings, permitting the stack to be assembled with the binder by inserting the rings through respective perforations in the stack.
A conventional binding machine typically includes a plurality of movable L-shaped hooks and a non-pivotal, stationary comb member with a plurality of spaced tines. The spine of the binding element is supported against the comb member so that the tines of the comb are alternatingly positioned between the rings of the binding element. While the stationary comb member holds the spine of the binding element, the hooks move in unison to cooperatively engage an inner side of the curled rings and then uncurl the rings away from the spine, spreading open the binding element.
Such a binding machine having a stationary comb member employs a conventional binding mechanism which moves the hooks through predetermined planar motions. In particular, the conventional binding mechanism moves hooks as follows: (1) the hooks first shift in unison in an axial direction (parallel to the comb member and the binding element) to individually engage respective rings of the binding element; and then (2) the hooks move in unison perpendicularly away from the comb member to pull and deflect the rings. These deflected rings are "uncurled" together until their free ends are accessible to be inserted through the series of punched perforations in the stack of pages.
In order to achieve the desired hook motion relative to the stationary comb member, a prior art binding mechanism typically has a flat plate drivable to slide under a planar work surface adjacent the stationary comb member, so that the plate is moveable in a plane parallel to the work surfaces. The hooks are fixed to the moveable plate, extending upwardly through a series of grooves in the work surface. Because the hooks are fixed to move with the sliding plate, the hooks have a planar movement from a position near the comb element, shifting axially and then sliding transversely away from the comb element. After the punched pages are assembled onto the rings, the described conventional hook motion is reversed, permitting the rings to curl back to their original shape and closing the binding element. Such a conventional binding machine having a stationary comb and planar-movable hooks is disclosed in U.S. Pat. No. 5,419,668, incorporated herein by reference in its entirety.
To cause the axial shift of the hooks for engaging and releasing the rings, the conventional binding mechanism includes a cam device which causes the plate to slide in a L-shaped pattern, resulting in the predetermined shifting and sliding hook motion. In another known binding machine, the comb member is axially shifted to move the binder rings into an engaged relation with the hooks, and the hooks are then linearly moved to spread open the rings of the binding element.
Binding machines are also known which have a stationary comb and rotary-moving hooks that uncurl the rings of a binding element against a stationary cylindrical-shaped surface.
Certain problems can arise with the described movable-hook style binding machines. Firstly, such machines can be complicated to manufacture because numerous parts are required to cause the planar hook motion. Secondly, the linear pulling motion of the hooks which uncurls the rings can sometimes cause an uneven degree of uncurling of rings along the length of the binder. This is known as "hook skew" which undesirably results in non-uniform or non-linear alignment of the free ends of the rings. This makes the insertion of the punched stack onto the rings difficult. Thirdly, the typical planar motion of the hooks uncurls the rings so that a linearly deflected portion of each ring is forced to lie flatly against the planar unrolling surface. Because of the rearward curvature of relaxed portions of the rings, their the free ends tend to angle rearwardly, and therefore, a substantial length of each ring must be flatly uncurled in order to achieve a suitable angle for accessing the free ends.
It is, therefore, an object of the present invention to provide a binding machine that is easy to use and which minimizes nonuniform opening of a binding element.
A further object of the invention is to provide a binding machine that has few parts which is easy to manufacture and assemble.